Otitis media (OM) is the most common reason that an ill child visits a health care provider or undergoes a general anesthetic. OM is also the most common reason that a child receives an oral antibiotic and the over-treatment of patients with OM has been suspected of contributing to the development of antimicrobialresistant organisms. OM disproportionately affects socio-economically disadvantaged children, Native American children and is a factor that inhibits women from full participation in the workforce. The major focus of our laboratory for the past decade has been elucidating the path physiology of chronic OM with the ultimate goal of developing more effective treatments. During this time, we have shown that chronic OM is not a purely inflammatory process, but rather is a bacterial biofilm illness. The recognition that OM is a biofilm disease then led to a novel hypothesis: The Distributed Genome Hypothesis. This hypothesis states that there is a supra-genome for pathogenic bacteria and that each individual bacterium possesses only a subset of genes from the supra-genome. The supra-genome is a reservoir for panoply of contingency genes that collectively provides a significant survival benefit for the population-at-large. In this continuing application we specifically test the Distributed Genome Hypothesis in Haemophilus influenza (HI) with four Specific Aims: 1) Perform comparative genomic studies among clinical isolates of HI To characterize the extent of genomic plasticity; 2) Determine the extent of HI inter-isolate recombination during the infectious process; 3) Prepare transformation knockouts of HI and compare their survival time in vivo with wild-type congener strains; 4) Phenotypic characterization of HI biofilms. These Specific Aims will be accomplished by experiments using state-of-the-art high throughput genomic, molecular biology, imaging and modeling techniques, as well as investigations in children. Preliminary data generated from a micro array library composed of 10 clinical isolates of H. influenza demonstrated that H. influenza does indeed have a supra-genome that is twice the Size of a single bacterium. These findings shed light on many aspects of OM, including disease persistence in the fact of antibiotic treatment, and provide an explanation for the success of adenoidectomy in the management of OM.